Four Jewish community centers across the United States and a number of Anti-Defamation League offices have received bomb threats, the sixth such wave since the beginning of the year.

As of 9:30 a.m. Tuesday, Secure Community Network, the security arm of the Jewish Federations of North America, had reported threats called into community centers in Milwaukee; Rockville, Maryland, a suburb of Washington D.C.; Portland, Oregon; and Rochester, New York.

Meanwhile, the ADL confirmed that several of its regional offices had been threatened.

“We just received multiple #bombthreats at ADL offices,” ADL said on Twitter. “Law enforcement personnel are responding. More details to come.”

In Rochester, the evacuation of members and staff on Tuesday was ordered shortly before 6 a.m., the local ABC affiliate 13WHAM reported. About 75 people were evacuated from the building. Parents whose children attend the JCC day care were notified and asked to make alternate child care arrangements for the day, according to the Democrat & Chronicle newspaper.

Local and state police officers and FBI agents reportedly were on the scene to sweep the building.

The bomb threat comes less than a week after at least five headstones were toppled at the Waad Hakolel Cemetery, also known as the Stone Road Cemetery, in Rochester.

Also evacuated according to a Facebook posting was the JCC in Milwaukee, which also includes a day care center. It’s not clear if there were evacuations in Portland and in Rockville.

Paul Goldenberg, the SCN director, said that in every instance protocols were observed and went smoothly.

“The protocols and processes that these institutions have in place have gone smoothly,” he said. “Our constituents and members have remained safe.”

More than 100 Jewish institutions, mostly JCCs, have received bomb threats since the beginning of the year. The last two weeks saw vandalism at Jewish cemeteries in Philadelphia, St. Louis and Rochester, as well as two more waves of bomb threats called into JCCs, schools and institutions across the country, representing the fourth and fifth waves of such harassment this year. No explosive device was found after any of the calls.